ESP32

688 Articles

Linux, Running On Not A Lot

August 19, 2023 by 31 Comments

There are many possible answers to the question of what the lowest-powered hardware on which Linux could run might be, but it’s usually a pre-requisite for a Linux-capable platform to have a memory management unit, or MMU. That’s not the whole story though, because there are microcontroller-focused variants of the kernel which don’t require an MMU, including one for the Xtensa cores found on many Espressif chips. It’s this that [Naveen] is using to produce a computer which may not be the Linux computer with the lowest processor power, but could be the one consuming the least electrical power.

The result is definitely not a Linux powerhouse, but with its Arduino-sourced ESP32 board stacked on an UNO and I2C keyboard and display, it’s an extremely lightweight device. The question remains, though, is it more than a curiosity, and to what can it do? The chief advantage it has over its competitors such as the Raspberry Pi Zero comes in low power consumption, but can its cut-down Linux offer as much as a full-fat version? We are guessing that some commenters below will know the answer.

If you’re curious about the Xtensa version of Linux, it can be found here,

Off-Grid EV Charging

August 19, 2023 by 41 Comments

There are plenty of reasons to install solar panels on one’s home. Reducing electric bills, reducing carbon footprint, or simply being in a location without electric service are all fairly common. While some of those might be true for [Dominic], he had another motivating factor. He wanted to install a charger for his electric vehicles but upgrading the electric service at his house would have been prohibitively expensive. So rather than dig up a bunch of his neighbors’ gardens to run a new service wire in he built this off-grid setup instead.

Hooking up solar panels to a battery and charge controller is usually not too hard, but getting enough energy to charge an EV out of a system all at once is more challenging. The system is based on several 550W solar modules which all charge a lithium iron phosphate battery. The battery can output 100 A DC at 48 V which gives more than enough power to charge an EV. However there were some problems getting this much power through an inverter. His first choice let out the magic smoke when it was connected, and it wasn’t until he settled on a Growatt inverter capable of outputting 3.5 kW that the system really started to take shape.

All of this is fairly straightforward, but there’s an extra touch here that makes this project noteworthy. [Dominic] wanted to balance incoming power from the photovoltaic system to the current demands from the EVs to put less strain on the battery. An ESP32 was programmed to only send as much power to the EVs as the solar system is producing at any given time, and also includes some extra logic to make sure the battery doesn’t drain itself from the idle power requirements of the inverter. Right now the system works well but the true test will be when it goes through its first winter. Even though solar panels are more efficient at colder temperatures, if the amount of sunlight or the angle of the panels aren’t ideal there is generally much less production.

Smart Doorbell Focuses On Privacy

August 18, 2023 by 11 Comments

As handy as having a smart doorbell is, with its ability to remotely see who’s at the front door from anywhere with an Internet connection, the off-the-shelf units are not typically known for keeping user privacy as a top priority. Even if their cloud storage systems were perfectly secure (which is not a wise assumption to make) they have been known to give governmental agencies and police free reign to view the videos whenever they like. Unfortunately if you take privacy seriously, you might need to implement your own smart doorbell yourself.

The project uses an ESP32-CAM board as the doorbell’s core, paired with a momentary push button and all housed inside a 3D-printed enclosure. [Tristam] provides a step-by-step guide, including printing the enclosure, configuring the ESP32-CAM to work with the popular open-source home automation system ESPHome, handling doorbell notifications automatically, and wiring the components. There are plenty of other optional components that can be added to this system as well, including things like LED lighting for better nighttime imaging.

[Tristam] isn’t much of a fan of having his home automation connected to the Internet, so the device eschews wireless connections and batteries in favor of a ten-meter USB cable connected to it from a remote machine. As far as privacy goes, this is probably the best of all worlds as long as your home network isn’t doing anything crazy like exposing ports to the broader Internet. It also doesn’t need to be set up to continuously stream video either; this implementation only takes a snapshot when the doorbell button is actually pressed. Of course, with a few upgrades to the ESP circuitry it is certainly possible to use these chips to capture video if you prefer.

Thanks to [JohnU] for the tip!

UChaser Follows You Anywhere

August 15, 2023 by 16 Comments

If you’ve been making up for lost years of travel in 2023, you might have seen a fellow traveler in the airport terminal or train station walking with their luggage happily careening behind them. [Jesse R] and [Brian Lindahl] wanted more of that. They wanted an open-source, low-cost system that could be put in anything.

The basic principle is that they will have a transmitter that sends both a radio signal and an ultrasonic pulse. The receiver receives the radio signal and uses it as a reference for the two ultrasonic sensors. The time since the radio signal is compared between the two, and a distance and direction are established.

In practice, the radio is an ESP32-S3 using ESP-NOW (which we’ve seen relatively recently on another project), a protocol from Espressif that offers low latency 250 bytes payloads. The ultrasonic transceiver is based on Sparkfun’s HC-SR04. For prototyping purposes on the receiver, they just removed the transmitter to avoid populating the airwaves, as to listen, you had to transmit. The prototype was an electric wheelbarrow that would happily follow you around the yard wherever you go.

With the concept validated, they moved to a custom ultrasonic setup with a custom buffer amp and damp transistor, all centered around 20kHz. The simulations suggested they should have been better than the HC-SR04 from Sparkfun, but the 30-foot (9 meters) range went to 10 feet (3 meters). They ultimately returned to using Sparkfun’s circuit rather than the custom amp.

We’re looking forward to seeing the project continue. There are various challenges, such as variability in the speed of sound, echos and reflections, and ultrasonic line of sight. We love the peak behind the curtain that allows us to see what decisions get made and the data that informs those decisions. All the code and PCB design files are available on GitHub under an MIT and Creative Common license, respectively. This project was submitted as part of the 2o23 Hackaday Prize.

Video after the break.

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Weather Station With Distributed Sensors

August 11, 2023 by 2 Comments

Building a weather station is a fairly common project that plenty of us have taken on, and for good reason. They can be built around virtually any microcontroller or full-scale computer, can have as many or few sensors as needed, and range from simple, straightforward projects to more complex systems capable of doing things like sending data off to weather services like Weather Underground. This weather station features a few innovations we don’t often see, though, with a modular and wireless design that makes it versatile and easy to scale up or down as needed.

Each of the modules in this build use the ESP32 platform, which simplifies design and also takes care of the wireless capability needed. The base station gets a few extra sensors including those for carbon dioxide, volatile organic compounds, and nitrogen oxides. It also includes a screen which can be used to display a wide variety of data gathered locally but also includes forecast information fetched from the free OpenWeatherMap API. For the sensor modules, BME280 sensors are used for temperature, pressure, and humidity and each module includes its own solar panel and battery with the ESP32 chips set to operate using as little energy as possible.

One of the things that helps easily integrate all of the sensor modules is the use of ESP-NOW, which we have seen a few times before. It essentially eliminates the need for a router and allows ESP modules to connect directly with one another. The build also goes into detail about most of the aspects of this project including the programming of the GUI that the ESP32 base station displays on its screen, so for anyone looking to start their own weather station project this should be an excellent guide. Make sure to check out this one as well if you want to send all of your weather data to Weather Underground.

An Open Firmware For LILYGO’s E-ink Smart Watch

August 6, 2023 by 22 Comments

The world’s first quartz wristwatches were miles ahead of electric and mechanical wristwatches by most standards of the time, their accuracy was unprecedented and the batteries typically lasted somewhere on the order of a year. Modern smart watches, at least in terms of battery life, have taken a step backwards — depending on use, some can require daily charging.

If you’re looking to bridge the gap between a day and a year, you might look into a smart watch with an e-ink display. One option is the ESP32-based LILYGO T-Wrist. Of course, it’s not a smart watch without some software to run on it, which is where qpaperOS comes in.

Developed by [qewer33], this open source firmware for the T-Wrist is designed to get the most out of the battery by updating only once per minute. With a 250 mAh battery, it should last about five days on a charge. Of course, with the power of the ESP32 comes a whole host of other features including GPS, a step counter, and a weather display, although since the firmware is still under development, some of these features have yet to be implemented.

With all of the code available, qpaperOS could make an excellent platform from which to build your own smart watch around. Or perhaps you could chip in and add some of the features on the whislity. The ESP32 is a capable and versatile chip, even capable of playing popular 8-bit video games, although we’re not sure this functionality would fit in a smart watch and preserve battery life at the same time.

The ESP32 Doesn’t Need Much

July 28, 2023 by 19 Comments

For those looking to add wireless connectivity to embedded projects or to build IoT devices, there is perhaps no more popular module than the ESP32. A dual-core option exists for processor intensive applications, the built-in WiFi and Bluetooth simplify designs, and it has plenty of I/O, memory, and interoperability for most applications. With so much built into the chip itself, [atomic14] wondered how much support circuitry it really needed and set about building the most minimalist ESP32 development board possible.

Starting with the recommended schematic for the ESP32, the most obvious things to remove are a number of the interfacing components like the USB to UART chip and the JTAG interface. The ESP32 has USB capabilities built in, so the data lines from a USB port can be directly soldered to the chip instead of using a go-between. A 3.3V regulator eliminates the need for many of the decoupling capacitors, and the external oscillator support circuitry can also be eliminated when using the internal oscillator. The only thing [atomic14] adds that isn’t strictly necessary is an LED connected to one of the GPIO pins, but he figures the bare minimum required to show the dev board can receive and run programs is blinking an LED.

Building the circuit on a breadboard shows that this minimalist design works, but instead of building a tiny PCB to solder the ESP32 module to he attempted to build a sort of dead-bug support circuit on the back of the ESP32. This didn’t work particularly well so a tiny dev board was eventually created to host this small number of components. But with that, the ESP32 is up and running. These modules are small and compact enough that it’s actually possible to build an entire dev board setup inside a USB module for a Framework laptop, too.

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